PHYLOGENY OF GEOMYDOECUS AND THOMOMYDOECUS POCKET GOPHER LICE (PHTHIRAPTERA, TRICHODECTIDAE) INFERRED FROM CLADISTIC-ANALYSIS OF ADULT AND FIRST INSTAR MORPHOLOGY

The phylogeny for all 122 species and subspecies of chewing lice of th e genera Geomydoecus and Thomomydoecus (Phthiraptera: Trichodectidae) hosted by pocket gophers (Rodentia: Geomyidae) is estimated by a cladi stic analysis of fifty-eight morphological characters obtained from ad ults and first instars. The data set has considerable homoplasy, but s till contains phylogenetic information. The phylogeny obtained is mode rately resolved and, with some notable exceptions, supports the specie s complexes proposed by Hellenthal and Price over the the last two dec ades. The subgenera G. (Thaelerius) and T. (Thomomydoecus) are both sh own to be monophyletic, but the monophly of subgenus T. (Jamespattoniu s) could not be confirmed, perhaps due to the lack of first-instar dat a for one of its component species. The nominate subgenus of Geomydoec us may be monophyletic, but our cladogram was insufficiently resolved to corroborate this. Mapping the pocket gopher hosts onto the phylogen y reveals a consistent pattern of louse clades being restricted to par ticular genera or subgenera of gophers, but the history of the host-pa rasite association appears complex and will require considerable effor t to resolve.